My wife told me that the coolant level light would come on at odd times on
our 85 vanagon.  The level was OK but I changed out the tank sender anyway.
No improvement.  I asked around and a couple of VW places questioned if the
85 actually has a relay for the coolant level light.  "Did'nt that start in 86?"
they would say.  Also some thought it was the voltage requlator that was bad.
I found a book which lists all the relays for 80-85 Vanagons and there was
the relay listing.  But where is the mounting location?  It was'nt right
above the fuse block.  i spent about 30 minutes paging through the Bentley
manual and came upon a picture an air duct hose which had a relay near it.
I reached under the dash board and put my hand on top of the driver side air
duct and felt two small boxes.  I wiggled one loose and it was the coolant
level relay.  I replaced it and the light only comes on a start up.

I hope this information is helpful to someone out there.

Best,
Bill